HarperCollins Publishers, Inc.

Chapter One

Entryway Passages: Demystifying Dimensions

"Ike, I'm not so sure about this story I'm writing. I'm considering adding more dimensions. What do you think of that idea?"

"Athena, your big brother knows very little about fixing stories. But odds are it won't hurt to add new dimensions. Do you plan to add new characters, or flesh out your current ones some more?"

"Neither; that's not what I meant. I plan to introduce new dimensions — as in new dimensions of space."

"You're kidding, right? You're going to write about alternative realities — like places where people have alternative spiritual experiences or where they go when they die, or when they have near-death experiences?* I didn't think you went in for that sort of thing."

"Come on, Ike. You know I don't. I'm talking about different spatial dimensions — not different spiritual planes!"

"But how can different spatial dimensions change anything? Why would using paper with different dimensions — 11 X 8 instead of 12 X 9 , for example — make any difference at all?"

"Stop teasing. That's not what I'm talking about either. I'm really planning to introduce new dimensions of space, just like the dimensions we see, but along entirely new directions."

"Dimensions we don't see? I thought three dimensions is all there are."

"Hang on, Ike. We'll soon see about that."

The word "dimension," like so many words that describe space or motion through it, has many interpretations — and by now I think I've heard them all. Because we see things in spatial pictures we tend to describe many concepts, including time and thought, in spatial terms. This means that many words that apply to space have multiple meanings. And when we employ such words for technical purposes, the alternative uses of the words can make their definitions sound confusing.

The phrase "extra dimensions" is especially baffling because even when we apply those words to space, that space is beyond our sensory experience. Things that are difficult to visualize are generally harder to describe. We're just not physiologically designed to process more than three dimensions of space. Light, gravity, and all our tools for making observations present a world that appears to contain only three dimensions of space.

Because we don't directly perceive extra dimensions — even if they exist — some people fear that trying to grasp them will make their head hurt. At least, that's what a BBC newscaster once said to me during an interview. However, it's not thinking about extra dimensions but trying to picture them that threatens to be unsettling. Trying to draw a higher-dimensional world inevitably leads to complications.

Thinking about extra dimensions is another thing altogether. We are perfectly capable of considering their existence. And when my colleagues and I use the words "dimensions," and "extra dimensions," we have precise ideas in mind. So before taking another step forward or exploring how new ideas fit into our picture of the universe — note the spatial phrases — I will explain the words "dimensions" and "extra dimensions" and what I will mean when I use them later on.

We'll soon see that when there are more than three dimensions, words (and equations) can be worth a thousand pictures.